Quantum noise observation and control A. HeidmannM. PinardJ.-M. Courty P.-F. CohadonT. Briant O. Arcizet T. CaniardJ. Le Bars Laboratoire Kastler Brossel, Paris

1980 – 90: Radiation pressure effects limit the sensitivity Studies on ideal systems Study of quantum noise in interferometers 1990 – 2000: Reduction of noise by quantum optics techniques (squeezing, QND)

Experimental injection of squeezing in an interferometer Study of quantum noise in interferometers McKenzie et al., Phys. Rev. Lett. 88, (2002) Since 2000:Application to GW interferometers

Study of quantum noise in interferometers Adaptation of squeezing Constraints on the interferometer (losses, …) Needs for: New (simpler ?) schemes Experimental tests of quantum noise Theoretical studies Kimble et al., Phys. Rev. D 65, (2002)

Output phase-shift: Quantum noises in interferometers Mirror motion:

Noise reduction by squeezing Squeezing of a specific combination of   in and  I in   Frequency dependent squeezing

  Frequency dependent quadrature Noise reduction by QND measurement Measurement of a specific combination of   out and  I out Quantum correlations in the interferometer

Insensitive to quantum properties of the interferometer New scheme: quantum locking of mirrors Local measurement and active control of mirror motion Courty et al., Phys. Rev. Lett. 90, (2003)

Interferometer: Finesse = 600 Input = 20 W Interferometer sensitivity

Control cavity: Finesse = Input = 5 mW Measurement of   x m limited by   in and   x r Measurement of mirror motion

Optimal gain: large at low freq. small at high freq. Control with an optimal gain Mirror is locked to the reference mirror Reduction of radiation pressure noise

Locking with QND measurement Control cavity: QND measurement 1% loss Noise reduction below SQL No effect of interferometer losses

Signal amplification by cavity detuning Noise reduction in signal recycled interferometers Similar effect expected by cavity detuning Modification of mirror dynamics Amplification of signal Buonnano, Chen, Phys. Rev. D 64, (2001)

Sensitivity improvement by cavity detuning Signal amplification by the mirror dynamics Possible implementation in GW interferometers Test with our experiment

Measurement of small displacements Optomechanical sensor based on a high-finesse cavity (30 000) Quantum limited sensitivity:

Current improvements of the experiment New cavity with a finesse Improvement of the laser frequency locking Cryogenic setup Sensitivity improved by a factor 10

Comprehensive study of quantum noise with real systems Interferometer constraints, active controls, detection,... Search for innovative and simpler quantum optics methods Quantum locking of mirrors, … Experimental observation and tests of quantum noise Up to now, no observation of radiation pressure effects Tests of quantum noise reduction schemes Development of efficient squeezing sources Conclusion – Main issues